IBS stands for Irritable Bowel Syndrome. It is a common, chronic disorder that affects the large intestine (colon). IBS is classified as a functional gastrointestinal disorder because it involves a problem with how the brain and the gut work together, rather than structural damage to the bowel itself.

Key Characteristics

IBS is defined by two key symptoms:

Chronic abdominal pain or discomfort.

Pain that is related to a change in bowel habits (either improving or worsening after a bowel movement).

Main Symptoms

Symptoms vary greatly but typically involve:

Abdominal pain, cramping, or bloating.

Altered bowel habits, which are used to classify the specific type of IBS:

IBS-C (Constipation-dominant): Hard, lumpy stools.

IBS-D (Diarrhea-dominant): Loose, watery stools, often with urgency.

IBS-M (Mixed): Alternating periods of constipation and diarrhea.

Excess gas.

Feeling of incomplete evacuation after a bowel movement.

Mucus in the stool.

Causes and Triggers

The exact cause is unknown, but it is believed to be a disorder of gut-brain interaction (the nervous system linking the brain and gut). Factors contributing to IBS include:

Hypersensitive Colon: An overly sensitive large intestine that reacts strongly to normal events (like eating).

Dysmotility: Abnormal muscle contractions in the intestine (too fast or too slow).

Infections: IBS can sometimes develop after a severe bout of gastroenteritis (post-infectious IBS).

Stress: Emotional distress and anxiety can trigger or worsen symptoms.

Diet: Certain foods (like high-FODMAP foods) can trigger symptoms.

Diagnosis

Diagnosis is typically made based on symptoms (using criteria like the ROME IV criteria), and by ruling out other conditions. Doctors may perform tests (blood tests, colonoscopy) to exclude issues like Celiac disease, inflammatory bowel disease (IBD), or infections, especially if "red flag" symptoms are present (e.g., unexplained weight loss, blood in stool, anemia)